Limitation of Genera among the Hydroida. 371 



II. 



Synopsis of the Genera and Species of Campanularian Hydroids 

 with known trophosomes. 



CampaimlaridaB. 

 1. Campanularia, Lamarck (in part). 



Trophosome. — Hydrocaulus simple or branching, rooted by 

 a creeping filiform hydrorhiza ; hydrothecse bell-shaped, with an 

 entire or serrated margin, and destitute of an operculum ; tenta- 

 cles surrounding the base of a large, very contractile metastome. 



Gonosome. — Gonangium seated either on the hydrorhiza or 

 hydrocaulus, and containing phanerocodonic gonophores. Um- 

 brella, at the time of liberation, deep bell-shaped ; manubrium 

 of moderate size, with the mouth provided with four shallow 

 lips, or simple ; radiating canals four ; marginal tentacles four, 

 with bulbous bases, destitute of ocelli; lithocysts eight, two in 

 each interradial space, and never developed upon the base of a 

 tentacle; generative elements developed in special sporosacs, 

 which are borne as buds on the radiating canals. 



As the Medusa advances towards maturity, the marginal ten- 

 tacles increase in number, and the oral lobes of the manubrium 

 become more decided. 



The name of Campanularia was originally applied by Lamarck to 

 certain Hydroids which had been a short time previously distributed 

 by Lamouroux under two generic names, Clytia and Laomedea. 

 The genera Clytia and Laomedea, as defined by Lamouroux, were 

 constructed on insufficient and imperfectly comprehended characters, 

 and cannot stand ; while, at the same time, Lamarck's genus Cam- 

 panularia involves two distinct generic types. For one of these 

 types the name of Campanularia ought to be retained, while for the 

 other we may choose between Clytia and Laomedea of Lamouroux. 

 Laomedea, however, has been in more general use among authors, 

 and it will therefore be convenient to retain it ; while Clytia, which 

 includes only forms referable to Campanularia or to Laomedea, must 

 accordingly be suppressed. 



The Medusa of Campanularia, as this genus is here defined, is 

 referable to a part of Gegenbaur's genus Eucope. The Medusae in- 

 cluded by Gegenbaur under this name belong to two distinct types, 

 — one distinguished, in its mature state, by its deep bell-shaped 

 umbrella, its comparatively small number of marginal tentacles, and 

 the position of the lithocysts in the centre of the interval between 

 two tentacula ; the other by its shallow, almost disc-shaped umbrella, 

 its very numerous tentacula, with reentrant bases, and the position 

 of the lithocysts — each on the inner side of the base of a tentacle. 

 This latter group comprises the forms to which P^ron and Lesueur 

 had long ago given the name of Obelia ; while, if Eucope be retained 

 as a generic appellation, it must be confined to the former. 



